In recent years, development of energy-saving products and energy-saving techniques is in progress in every industry with regard to electric power shortage and so on. Vacuum insulation panels are products developed as one of energy-saving measures. At present, the panels are widely adopted as a heat insulating material for refrigerators, vending machines, and the like and for heat insulating performance enhancement and electric power consumption reduction. Also in progress is examination for application as a heat insulating material for houses. In general, existing vacuum insulation panels have a structure in which a core member such as glass wool is heat sealed with an aluminum laminate film.
In a vacuum insulation panel heat sealed with an aluminum laminate film, moisture permeation from a heat seal portion results in a decrease in the degree of vacuum, and enclosure with an adsorbent such as activated carbon and zeolite is performed in this regard. Even so, a problem arises as the heat insulating performance is halved in seven to eight years. Desired in this regard is development of a vacuum insulation panel capable of maintaining its heat insulating properties for a long time. Developed as a vacuum insulation panel having long-term heat insulation properties is a vacuum insulation panel that is evacuated inside and has a stainless steel-based end portion welded in a state where a core member such as glass wool is wrapped with a thin metal plate such as a stainless steel plate.
Patent Document 1 discloses a method for manufacturing such vacuum insulation panels. In the method, a heat insulating material is arranged in the space that is formed by an inner plate body and an outer plate body provided with an evacuation port, a laminated body is prepared in which the peripheral edge portions of the outer and inner plate bodies are welded, a sealing member is placed on the wax that is arranged around the evacuation port, the laminated body is arranged in a chamber, vacuum suctioning is performed from the evacuation port by a vacuum suction unit, the wax is melted by heating of the laminated body, and the evacuation port is sealed by the sealing member.
Patent Document 2 discloses a vacuum insulation panel manufacturing method by which a heat insulating material that has a thick-walled region and a thin-walled region is arranged in a substantially flat plate-shaped space formed in a metallic plate-shaped body and evacuation is performed from an evacuation port provided in a place laminated with the thin-walled region of the metallic plate-shaped body.
Patent Document 1: Japanese Patent No. 4365736
Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2001-311497